source: NonGTP/OpenEXR/include/IlmImf/ImfChromaticities.h @ 855

///////////////////////////////////////////////////////////////////////////
//
// Copyright (c) 2003, Industrial Light & Magic, a division of Lucas
// Digital Ltd. LLC
// 
// All rights reserved.
// 
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
// *       Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// *       Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// *       Neither the name of Industrial Light & Magic nor the names of
// its contributors may be used to endorse or promote products derived
// from this software without specific prior written permission. 
// 
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
///////////////////////////////////////////////////////////////////////////


#ifndef INCLUDED_IMF_CHROMATICITIES_H
#define INCLUDED_IMF_CHROMATICITIES_H

//-----------------------------------------------------------------------------
//
//      CIE (x,y) chromaticities, and conversions between
//      RGB tiples and CIE XYZ tristimulus values.
//
//-----------------------------------------------------------------------------

#include <ImathVec.h>
#include <ImathMatrix.h>

namespace Imf {

   
struct Chromaticities
{
    Imath::V2f  red;
    Imath::V2f  green;
    Imath::V2f  blue;
    Imath::V2f  white;

    Chromaticities (const Imath::V2f &red   = Imath::V2f (0.6400f, 0.3300f),
                    const Imath::V2f &green = Imath::V2f (0.3000f, 0.6000f),
                    const Imath::V2f &blue  = Imath::V2f (0.1500f, 0.0600f),
                    const Imath::V2f &white = Imath::V2f (0.3127f, 0.3290f));
};


//
// Conversions between RGB and CIE XYZ
//
// RGB to XYZ:
//
//      Given a set of chromaticities, c, and the luminance, Y, of the RGB
//      triple (1,1,1), or "white", RGBtoXYZ(c,Y) computes a matrix, M, so
//      that multiplying an RGB value, v, with M produces an equivalent
//      XYZ value, w.  (w == v * M)
// 
//      If we define that
// 
//         (Xr, Yr, Zr) == (1, 0, 0) * M
//         (Xg, Yg, Zg) == (0, 1, 0) * M
//         (Xb, Yb, Zb) == (0, 0, 1) * M
//         (Xw, Yw, Zw) == (1, 1, 1) * M,
// 
//      then the following statements are true:
// 
//         Xr / (Xr + Yr + Zr) == c.red.x
//         Yr / (Xr + Yr + Zr) == c.red.y
// 
//         Xg / (Xg + Yg + Zg) == c.red.x
//         Yg / (Xg + Yg + Zg) == c.red.y
// 
//         Xb / (Xb + Yb + Zb) == c.red.x
//         Yb / (Xb + Yb + Zb) == c.red.y
// 
//         Xw / (Xw + Yw + Zw) == c.red.x
//         Yw / (Xw + Yw + Zw) == c.red.y
// 
//         Yw == Y.
// 
// XYZ to RGB:
// 
//      YYZtoRGB(c,Y) returns RGBtoXYZ(c,Y).inverse().
// 
// Warning:
// 
//      It would seem that RGBtoXYZ() and XYZtoRGB() are all you need
//      to convert RGB values with one set of primary and white point
//      chromaticities into perceptually equivalent RGB values with
//      different primary and white point chromaticities:
// 
//          M44f M = RGBtoXYZ (chromaticities1, Y1) *
//                   XYZtoRGB (chromaticities2, Y2);
// 
//      However, this simple conversion does not account for white point
//      adaptation, and produces undesirable results.  The proper thing
//      to do is to perform a Bradford or a von Kries transform, which
//      moves the white point of the original color space to the white
//      point of the destination color space, dragging other colors with
//      it in a sensible fashion.  
//

Imath::M44f     RGBtoXYZ (const Chromaticities chroma, float Y);
Imath::M44f     XYZtoRGB (const Chromaticities chroma, float Y);


} // namespace Imf

#endif